Chemical Analysis

• What is one way to determine if a substance is pure?

  Testing its melting or boiling point
• What is a formulation in chemistry?

  A mixture designed for a specific purpose
• What is chromatography used for?

  Separating substances in a mixture
• What is the stationary phase in chromatography?

  Special chromatography paper or filter paper
• What is the mobile phase in chromatography?

  Water that rises up the paper
• Why is a pencil line drawn at the bottom in chromatography?

  So it doesn't move with the solvent
• How is the RF value calculated in chromatography?

  Distance moved by spot / distance moved by solvent
• What sound does hydrogen gas make when tested with a burning splint?

  Squeaky pop
• What happens when oxygen is tested with a glowing splint?

  It relights the splint
• What happens when carbon dioxide is bubbled through lime water?

  It turns the lime water cloudy
• What happens when chlorine gas is tested with damp blue litmus paper?

  It bleaches the paper white
• What color flame does lithium produce in a flame test?

  Crimson
• What color flame does sodium produce in a flame test?

  Yellow
• What color flame does potassium produce in a flame test?

  Lilac
• What color flame does calcium produce in a flame test?

  Orange-red
• What color flame does copper produce in a flame test?

  Green
• What happens when sodium hydroxide is added to a solution containing aluminium ions?

  A white precipitate forms, then dissolves with excess NaOH
• What color precipitate does copper(II) ions form with sodium hydroxide?

  Blue
• What color precipitate does iron(II) ions form with sodium hydroxide?

  Green
• What color precipitate does iron(III) ions form with sodium hydroxide?

  Brown
• What gas is produced when carbonates react with acids?

  Carbon dioxide
• What is the color of silver chloride precipitate?

  White
• What is the color of silver bromide precipitate?

  Cream
• What is the color of silver iodide precipitate?

  Yellow
• What is the color of the precipitate formed when sulfate ions react with barium chloride and hydrochloric acid?

  White
• What are the advantages of instrumental methods in chemical analysis?

  Accurate, sensitive, and fast
• What is flame emission spectroscopy used for?

  Identifying metal ions by their emission spectra
• What are the steps involved in chromatography?

  1. Draw a pencil line at the bottom of the paper
  2. Apply the sample to the line
  3. Place the paper in the solvent
  4. Allow the solvent to rise up the paper
  5. Measure the distance moved by the solvent and the spots
  6. Calculate the RF value
• What are the key chemical tests mentioned?

  • Test for hydrogen: squeaky pop with a burning splint
  • Test for oxygen: relights a glowing splint
  • Test for carbon dioxide: turns lime water cloudy
  • Test for chlorine: bleaches damp blue litmus paper
  • Flame tests for metals: lithium (crimson), sodium (yellow), potassium (lilac), calcium (orange-red), copper (green)
  • Test for metal ions in solution: add sodium hydroxide (aluminium, calcium, magnesium form white precipitates; copper forms blue; iron(II) forms green; iron(III) forms brown)
  • Test for carbonates: react with acids to produce carbon dioxide
  • Test for halide ions: mix with silver nitrate and nitric acid (chloride forms white, bromide forms cream, iodide forms yellow)
  • Test for sulfate ions: mix with barium chloride and hydrochloric acid to form a white precipitate
• What are the advantages of instrumental methods over traditional chemical tests?

  • More accurate
  • More sensitive
  • Faster
  • Can identify substances more precisely
• What is flame emission spectroscopy?

  • A method to identify metal ions
  • Light from a flame is passed through a spectroscope
  • Identifies wavelengths emitted by metal ions
  • Produces an emission line spectrum